A biosensor is an analytical device which utilizes an intrinsic function of a biological body to examine properties of biological materials. The biosensor is excellent in sensitivity and reaction specificity since it uses a biological material as a detecting element. Thus, the biosensor is used in a variety of fields such as medical/medicine (clinical chemistry analysis and treatment), process measurement of bio-industry, environmental measurement, stability evaluation of chemicals and the like, and its applicable range is being continuously extended. particularly, the biosensor is widely used to analyze a biological sample including blood in the medical diagnosis field. The biosensor is classified into an enzyme analysis type and an immunity analysis type according to the kind of a detecting element, and is classified into an optical biosensor and an electrochemical biosensor according to a method of quantitatively analyzing a target substance in a biological sample.
The biosensor of enzyme analysis type employs specific reactions between enzyme and substrate, or specific reactions between enzyme and enzyme inhibitor. The biosensor of immunity analysis type employs specific reactions between antigen and antibody. Thus, the biosensor of immunity analysis type is widely used in hospital and clinical chemistry analysis fields since it is excellent in measurement sensitivity and can rapidly obtain a result. particularly, a target substance can be quantitatively analyzed directly on the spot through a disposable biosensor and a small-sized readout meter in the point-of-care testing (POCT).
The optical biosensor has been most widely used, and it can measure a concentration of a target substance through measurement of optical transmittance, optical density or wavelength change. The optical biosensor has an advantage in that the reaction mechanism of various substances to be analyzed has been already found, and a variation in the measurement time is small since measurement is performed after reaction for a sufficient time. However, the optical biosensor entails problems in that it has a relatively long measurement time and requires a large quantity of samples as compared to the electrochemical biosensor. Also, the optical biosensor encounters drawbacks in that a measurement result is affected by turbidity of the sample and miniaturization of an optical section is difficult. The electrochemical biosensor detects an electrical signal obtained from a reaction to measure a concentration of a target substance.
The electrochemical biosensor has advantages in that amplification of a signal is possible with only an infinitesimal sample, its miniaturization is easily achieved, a measurement signal can be stably acquired, and its incorporation with information communication devices is easily accomplished. However, it has still shortcomings in that an electrode process is required, the production cost is high and the measurement signal is very susceptible to the reaction time.
The use of a readout meter requires that a biosensor should be inserted into the readout meter. When the biosensor is inserted into the readout meter, the meter recognizes the insertion of the biosensor thereto and analyzes a target substance in a sample. In this case, it is required that a calibration code programmed in the readout meter should be selected, and information on target substance to be detected by the inserted biosensor should be provided. Thus, a conventional biosensor and readout meter employs a scheme of transforming a biosensor structure and electrode, or allowing a user to directly enter information to the readout meter.
EP 0471986 discloses a quantitative analysis system which measures the level of glucose in blood using a disposable biosensor. In the above European Patent, a resistance value between a pair of electrodes is measured to determine whether blood is injected into the biosensor so as to commence the measurement of the blood glucose level, and a resistor is connected between the electrodes to change a measurement mode for the meter to select a required calibration curve. However, this European Patent has an inconvenience in that electrodes connected with a resistor must be used independently of the biosensor. U.S. Pat. No. 4,999,582 to Parks et al. discloses a biosensor electrode excitation circuit which determines whether a biosensing test cell as a biosensor has been inserted into a biosensing instrument, and applies an excitation voltage between a pair of electrodes of the test cell based on the determination result. U.S. Pat. No. 5,438,271 to White et al. discloses a readout meter determines whether a sample strip as a biosensor has been properly inserted into the readout meter, and distinguishes whether a sample strip is for test or for calibration of the readout meter. U.S. Pat. No. 6,599,406 B1 to Kawanaka et al. discloses a concentration measuring apparatus which determines the kind of a target component to be measured and whether the test strip has been inserted into the measuring apparatus, by forming a separate identifying electrode. U.S. Pat. No. 6,827,829 B2 to Kawanaka et al. discloses a test strip for concentration measuring apparatus in which a separate reagent identifying electrode is formed on the test strip in various fashions to determine the kind of a target component to be measured and whether the test strip has been inserted into the measuring apparatus.
As mentioned above, the conventional biosensors and the readout meters implement functions of determining whether the biosensors have been inserted into the readout meters, the kind of the biosensors, analyte, and the like. However, there is a functional limitation since these functions are separately implemented, but not integrally implemented on the biosensors.